They are small songbirds, at most 12 cm long. In most subspecies, the underparts of both male and female are bright yellow, the backs are a dull brown color. The forehead, throat and upper breast of the adult male is a dark, metallic blue-black.

Originally from mangrove habitat, the Olive-backed sunbird has adapted well to humans, and is now common in fairly densely populated areas, even forming their nests in human dwellings.

In one instance, a couple of sunbirds built a nest in a potted plant(located along an HDB corridor) owned by one family in Sengkang and provided the family with an opportunity to observe the birth and growth of a sunbird youngling.